Re: [ff3d-users] Variational form of potential flow with free surface on mesh

[Thomas Ward]

Stephane

last May you gave me a pointer to how to work with periodic boundary 
conditions in ff3d. 8 months later I have found the time to try it.....

1.
I'm not able to get it to work, my file is attached at the end of this 
message can you see what I am doing wrong?

2.
I would like to understand how it is implemented in the code  have been 
trying to understand code but can't manage to follow it. Can you point 
me in the right directions, so far I have been looking through 
MeshPeriodizer.cpp and VerticesCorrespondance.cpp , Mesh.cpp and 
SurfaceMeshOfQuadrangles.cpp

I can see that the nodes of the end boundary of the structured mesh are 
mapped to the nodes of the start boundary but I am struggling to see how 
this is carried forwards to the solver.

Are there any papers which describe the method you have followed?



thanks for your help

Tom Ward.



vertex a = (0,0,0);
vertex b = (10,10,10);
vector n = (25,50,10);

mesh M = structured(n,a,b);
//this next line is the only change I made to the static solution
M = periodic(M,0:1);

double f=1.4;
function alpha=f*f/9.81;
solve(phi) in  M
 {
    test(w)
      int(grad(phi)*grad(w))
      +int[M zmax](w*alpha*phi)
      +int[M xmin](w*f)
      -int[M xmax](w*f)
      =0;
 };

save(vtk,"tank-varA-periodic",phi,M);

Thomas Ward wrote:

> Many thanks Stephane, 

> I hope to try the periodic conditions next week, its not totally clear 
> to me how the periodic mesh becomes a periodic boundary condition but I 
> will have a try first and then ask if I can't work it out.
>
>
> Tom
>
>
>
> Stephane Del Pino wrote:
......
> > > I'm about to try using periodic BC, I note from the mailing list that
> > > you were playing around with this a couple of years ago, do you have any
> > > sample files or other documentation or pointers to the source code?
> > Yes this is not a big deal in ff3d. Assume that M is your structured 
> > mesh, then
> >     M = periodic(M,0:1,2:3,4:5);
> > will create a triperiodic mesh where
> >     0 represents xmin,
> >     1 represents xmax,
> >     2 represents ymin,
> >     3 represents ymax,
> >     4 represents zmin,
> >     5 represents zmax,
> >
> >     M = periodic(M,2:3);
> > would create a periodic mesh in the direction y. Note that up to now M 
> > must be a structured mesh.